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Okuma Drive Units Repair
Component-level repair for VAC, MIV, MFU and BLD servo and spindle drive units — the power electronics that turn control commands into actual axis and spindle movement.
Photo coming soon
What Is Okuma Drive Units Repair?
The control tells the machine what to do; the drive unit is what actually makes it happen. Servo drives take the control's commands and turn them into precise axis movement, while spindle drives do the same for the main spindle motor — converting, amplifying and regulating power at levels the control's own electronics never touch. When a drive fails, the symptom is usually mechanical-looking: a jerky axis, a stalled spindle, an overload alarm — even though the actual fault is entirely electronic.
We work at component level here too. Inside a drive unit, that means power boards, control boards, IGBT output stages, gate drivers and the capacitors and fans that keep them cool. Okuma's drive lineup spans several genuinely different platforms over the decades — VAC-series spindle and servo drives, MIV inverter units, MFU and BLD amplifiers — and each has its own known failure points, which is exactly the kind of detail that makes board-level repair realistic instead of guesswork.
We are an independent repair company. We are not an authorized Okuma dealer, distributor or service partner — we repair Okuma drive electronics on customer-owned equipment, working from the symptoms and units you send us or that we inspect on-site.
This page covers the drive unit specifically. If the fault turns out to be in the control cabinet or the spindle mechanics instead, we handle those too — see CNC Control Repair and Spindle Repair for the rest of the picture. A stalled spindle, for instance, can just as easily be a drive fault as a bearing fault — which is exactly why diagnosis comes before any repair quote.
Drive faults tend to trace back to a handful of predictable causes: IGBT output transistors that short under sustained load, electrolytic capacitors that dry out over years of thermal cycling, cooling fans that seize and let heat build up unnoticed, and encoder signal paths that degrade from vibration or contamination. None of it is exotic — it's wear that shows up in specific, well-documented places.
Diagnosis at a Glance
A quick way to check whether your symptom points to the drive unit specifically, and which boards are typically involved before you ship anything.
Signs You Need This Service
Any of these usually point to a drive-side fault rather than a control or mechanical one.
- Motor turns jerky or vibrates under load
- Overload alarm even after the drive was checked
- Drive won’t power on, or turns on late
- Encoder error with an incorrect speed reading
- DC bus voltage alarms (over or under voltage)
- Drive overheating or a stalled cooling fan
What We Repair
Component-level work on the boards and modules inside the drive unit.
- MIV servo & spindle inverter drives
- VAC-series spindle drives (II / III)
- BLD brushless servo amplifiers
- MFU units and related power modules
- Power boards, control boards & gate drivers
- Cooling fans and power supply capacitors
Repairs cover drive units across every Okuma generation — from legacy VAC-series drives through current MIV inverter units. See our OSP controls guide for how drives typically pair with control generations.
What This Repair Covers
A closer look at each part of the drive unit we work on, from the power stage that drives the motor to the fans and capacitors that keep it cool.
Power Boards
Handles the raw current that drives the motor — the first place we look after an overload or overvoltage alarm.
Control Boards
Coordinates the drive's response to commands from the CNC control — separate from the power stage itself.
IGBT Output Stages & Gate Drivers
The switching transistors that shape motor current — a common failure point behind inverter bridge faults.
Encoder Feedback Circuits
Reads actual motor position and speed — a degraded signal path shows up as speed errors long before a hard failure.
Capacitors & Cooling Fans
Wear parts that quietly age with every duty cycle — often replaced preventively during any repair, not just when they fail.
DC Bus & Converter Link
The shared voltage link between drives in a multi-axis system — a frequent source of hard-to-trace voltage alarms.
How We Test a Repaired Drive
A drive repair isn't done when the board looks fixed — it's done when the unit has run under real load and proven it. Our process checks the power board, control board, connection boards, gate drivers and IGBT output stages, along with the drive's internal supply rails, before any repair is even attempted.
Once the actual fault is repaired, we don't stop at a bench test with no load. The unit runs on a test setup with the original or an equivalent motor, under monitored current, temperature, ripple and encoder signal conditions — then through an extended run under continuous load before it ships back. Preventive replacement of aging capacitors and fans happens at the same time, since sending a unit back that's likely to fail again in six months helps no one.
Every finding gets documented, with a final report and recommendations — so you know not just that it was fixed, but what actually failed and why.
Photo coming soon
What Makes Our Repair Different
A few things that shape how we approach every drive repair job, regardless of whether it's a legacy VAC unit or a current MIV inverter drive.
Diagnosis Before Quoting
We identify the actual failed component before giving you a price, not after. That means the quote reflects the real repair, not a guess based on the symptom alone.
Tested Under Real Load
A repaired drive runs with a motor under monitored load before it ships back, not just a static bench check.
Every Drive Generation Covered
From legacy VAC-series spindle drives through current MIV inverter units. We don't turn away a drive just because it predates the model you're currently running.
OSP Controls We Work Alongside
Drive units are control-generation-adjacent — the same VAC or MIV drive can pair with several different OSP generations depending on when the machine was built or last retrofitted. Knowing your control generation still helps us move faster. Find your specific generation below.
OSP-3000
Legacy LC series — tape and floppy-disk era controls.
OSP-5000LB/LC series — floppy disk and bubble memory era.
OSP-7000Cadet/Crown/early LB — full-size CRT-era displays.
OSP-U100LU/MX-V/MC-V/MA-V — transitional floppy-to-CF generation.
OSP-E100Last pre-THINC generation — no USB or Ethernet.
OSP-P100First P-series — open-architecture Windows-based control.
OSP-P200THINC-OSP global rollout — API and networking introduced.
OSP-P300Shared database, touchscreen — most common current-era control.
OSP-P500Current generation — Digital Twin, dual-core processing.
Okuma Models We Support
Drive repair is drive-model-specific rather than machine-model-specific — the same MIV unit can appear across several different Okuma machine families. Here are the model families we see most often.
LB & GENOS L
Lathes for shafts, gears and turned components.
GENOS M / MB & MAMachining centers for milled and prismatic parts.
MULTUS Mill-TurnMultitasking platforms machining complex parts in one setup.
MU-Series 5-AxisFive-axis centers for complex geometry and tight tolerances.
MCR Double-ColumnLarge-part machines for big, rigid workpieces.
MA-H HorizontalHorizontal centers built for long unattended runs.
Other Ways We Can Help
Drive repair is one part of what we do — here's the rest of the site if a different problem, or a different angle, fits your situation better.
CNC Control Repair
Board-level repair of OSP control boards, I/O modules and displays across every generation.
Spindle Repair
Bearing, encoder and winding repair to restore accuracy and extend spindle service life.
Every Component We Repair
Browse the complete catalog of boards, drives and modules we repair.
Automation & Robotics
Repair support for loaders, pallet systems, gantries and robot automation cells.
Spare Electronics
Tested spare boards and drives ready to ship when a fast swap beats a repair wait.
Industries We Serve
Automotive, aerospace, medical, defense and more — see how we support your sector.
Countries We Serve
See every country where we currently offer on-site technician visits.
All Services
Browse every repair and support service we offer, all in one place.
How This Repair Works
Three steps from a faulty drive to a load-tested, working one.
01
Send the Details
Machine model, drive model number, alarm codes or a description of what the drive is doing.
02
Diagnose & Quote
We identify the faulty component and give you a clear repair estimate before starting work.
03
Repair & Return
Component-level repair, full load test under monitored conditions, then shipped back or reinstalled on-site.
Frequently Asked Questions
No. We are an independent repair company, not an authorized Okuma dealer, distributor or service partner. We repair Okuma drive electronics on customer-owned equipment.
Not necessarily — jerky motion can come from the drive, the motor, or the encoder feedback path. Tell us the symptoms and any alarm codes and we'll help narrow it down before you ship anything.
Where practical, we test with the original or an equivalent motor under monitored load — not just a no-load bench check. That's what actually reveals whether a repair holds under real conditions.
Yes, for faults that need hands on the machine itself. See our country coverage for where we currently offer on-site visits.
Yes — legacy VAC-series drives are frequently expensive or impossible to source new, which makes component-level repair the realistic option rather than a fallback. Age alone is rarely a reason a drive can’t be repaired.
We'll tell you directly rather than bill for a repair that won't hold. Where a genuine repair isn't practical, we can discuss tested spare units through our spare parts service instead.
It depends on the fault and the platform, but we give you a realistic estimate as soon as diagnosis is complete — including time for the load test, which we don't skip to save a day.
Contact
Send us your machine details and drive symptoms — here's how to reach us directly.
Drive Acting Up? Tell Us the Symptoms
Machine model, drive model and what you're seeing — we'll help you figure out the fastest path back to production.
